Carnitine conjugates as dual prodrugs and uses thereof

ABSTRACT

The present invention discloses novel dual prodrug compositions of Formula 1, 
                         
wherein A is a single bond, —O—, or —CH 2 —; m and n vary from 0 to 15; p and q vary from 0 to 4; B is a single bond or —CR 3 R 4 ; D is selected from the group consisting —CO 2 R 5 , —OR 6 , —OCOR 7 , —SO 3 R 8 , —SO 2 NH 2 , —OPO(OR 9 )(OR 10 ), —OPO(OR 9 )(NH 2 ), —OPO(OR 9 )—O—PO(OR 10 )(OR 11 ),
 
                         
R 1  to R 11  are various substituents selected to optimize the physicochemical and biological properties such as, lipophilicity, toxicity, bioavailability, and pharmacokinetics of compounds of Formula 1. These compounds are useful for the treatment of various cardiovascular and neurological disorders.

This application claims benefit of priority of Provisional ApplicationNo. 60/518935, filed on Nov. 12, 2003.

FIELD OF THE INVENTION

This present invention relates to novel carnitine ester and etherconjugates of hypolipidemic agents and pharmaceutically acceptable saltsthereof. The novel compositions of the present invention are useful forthe treatment of cardiovascular diseases, metabolic diseases, obesity,diabetes, gastrointestinal disorders, inflammation, cancer, anemia,renal anemia, Alzheimer's diseasse; and for modulating peroxisomeproliferation by peroxisome proliferator-activated receptors (PPARs).

BACKGROUND OF THE INVENTION

It is to be noted that throughout this application various publicationsare referenced by Arabic numerals within brackets. Full citations forthese publications are listed at the end of the specification. Thedisclosures of these publications are hereby incorporated by referencein their entireties in order to more fully describe the state of the artto which this invention pertains.

Coronary heart-disease (CHD) is a leading cause of troublesome qualityof life, and mortality among the populations of the developed nationsand the economically fast-growing countries with worldwide reise inobesity, diabetes, including among young adults, due to high-caloriesdiets and poor exercise time. The cardiovascular disease ischaracterized by clogged arteries and reduced supply of blood andnutrients to the heart muscle caused by lipid deposition inside thearterial wall. Hyperlipidemia or hyperlipoproteinemia (formlipid-protein complexes) may be caused by genetic factors or by obesityand metabolic disorders. Lipid-protein complexes are sphericalaggregates consisting of a hydrophobic core composed of lipids(triglycerides and cholesterol esters) surrounded by hydrophilicexterior shell of about 2 nm composed of apoproteins, cholesterol, andphospholipids. The hydrophilic polar surface keeps the lipids dissolvedand circulating in the plasma. Based on the size and density, four mainlipoproteins prevalent in the plasma: chylomicrons, very low densitylipoprotein (VLDL), low density lipoprotein (LDL or LDL-C), and highdensity lipoprotein (HDL oar HDL-C). Chylomicrons and VLDL are rich intriglycerides and cholesterol. The are the sources of fatty acids inmuscles and adipose tissues. LDL-C particles are rich in cholesterol andare produced in the liver from dietary cholesterol, fromliver-synthesized cholesterol, and from remnants of chylomicrons andVLDL that have entered the extrahepatic tissues from the generalcirculation [1].

High levels of LDL-C (referred to as ‘bad cholesterol’) is a wellestablished major risk factor in CHD, but is effectively treated withHMG-CoA reductase inhibitors (statins) leading to substantial reductionin cardiovascular morbidity and mortality [2]. HDL-C particles (referredto as ‘good cholesterol’) are responsible for a cleansing mechanismcalled ‘reverse cholesterol transport,’ where the cholesterol istransported from extrahepatic tissues to the liver for catabolicdestruction and excretion. It is widely accepted that low levels ofHDL-C and high levels of triglycerides in plasma are important riskfactors contributing to CHD [3].

Levocarnitine (L-carnitine or vitamin B_(T)) belongs to a class of watersoluble vitamins which includes vitamin B-12,folic acid, biotin, vitaminB-6,and mevalonic acid. It occurs naturally, and serves as a cofactor infatty acid metabolism for energy production. This cofactor functions bybirding activated fatty acids in the form of acyl carnitine (carnitineshuttle). Use of 1-carnitine in the treatment of hyperlipoproteinemia,hyperlipidemia, and myocardial dysfunction has been the subject ofintensive investigation [4-9]. L-carnitine has also been reported to beuseful as an adjuvant therapy in the management of renal anemia [10].Propionyl carnitine (the propionic ester of carnitine) has been shown toimprove cardiac function [11, 12]. Acetyl carnitine has been proposed asa possible therapeutic agent for Alzheimer's disease [13]. Recently, CPS124,a carnitine monothiophosphate derivative which is a reversible andcompetitive inhibitor of carnitine palmitoyl transferase I, isreportedly undergoing clinical development for the treatment ofnon-insulin dependent diabetes mellitus (NIDDM) [14].

In humans, fibrates such as clofibrate, bezafibrate, fenofibrate,etofibrate, gernfibrozil, G10-2331,which are agonists of PPAR-alpha havebeen successfully used to treat hypertriglyceridemia. They function byincreasing the clearance and decreasing the synthesis of VLDL. Thefibtrates, however, have only a modest effect (10-20%) in increasingHDL-C levels [15, 16]. Clinical development of cardioprotective HDL-Celevating agents is a major current therapeutic goal. Recently, it wasshown that oxa substituted α,ω-alkanedicarboxylic acids and relatedcompounds raise serum HDL-levels significantly [17]. In particular,CI-1027 has been in clinical trials. Also, long chainα,ω-alkanedicarboxylic acids are also in clinical development ashypolipidemic agents [18,19].

In view of the extensive work in the treatment of hyperlipoproteinemia,hyperlipidemia, and myocardial dysfunction with L-camnitine, L-propionylcarnitine, CI-1027 and its analogs, and fibric acids, it is surprisingthat covalent conjugates of any two or more of these drugs have not beenproposed. Therefore, the present invention introduces a novel conceptreferred to as ‘double prodrug’ approach which involves the preparationof novel covalent conjugates comprising two or more drugs, and their usein the treatment of various cardiovascular disorders. A suitablecovalent attachment of two more of these cardiovascular agents will havea significant therapeutic value in that a single molecular entity mayhave multiple therapeutic effects resulting from diverse, butsynergistic mechanism of action, and controlled release of both drugs invivo through enzymatic hydrolysis of the conjugate. The concept of thepresent invention is not limited to cardiovascular applications; othertherapeutic applications, including CNS disorders, diabetes, cancer,inflammation, and the like are also contemplated.

SUMMARY OF THE INVENTION

The present invention discloses novel dual prodrug compositions ofFormula 1,

wherein A is a single bond, —O— or —CH₂—; m and n vary from 3 to 15; pand q vary from 0 to 4; B is a single bond or —CR³R⁴; D is selected fromthe group consisting of —CO₂R⁵, —OR⁶, —OCOR⁷, —SO₃R⁸, —SO₂NH₂,—OPO(OR⁹)(OR¹⁰), —OPO(OR⁹)(NH₂), —OPO(OR⁹)—O—PO(OR¹⁰)(OR¹¹),

R¹ to R¹¹ are various substituents selected to optimize thephysicochemical and biological properties such as, lipophilicity,toxicity, bioavailability, and pharmacokinetics of compounds ofFormula 1. These include, but are not limited to hydrogen, alkyl,alkenyl, alkynyl, cyloalkyl, acyl, hydroxyl, hydroxyalkyl, aryl, amino,aminoalkyl, alkoxyl, aryloxyl, carboxyl, halogen, alkoxycarbonyl,trihaloalkyl, cyano, and other suitable electron donating or electronwithdrawing groups.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides novel dual prodrug compounds and thecorresponding pharmaceutically acceptable salts thereof of Formula 1,

wherein A is a single bond, —O— or —CH₂—; m and n vary from 0 to 15;pand q vary from 0 to 4; B is a single bond or —CR³R⁴; D is selected fromthe group consisting of —CO₂R⁵, —OR⁶, —OCOR⁷, —SO₃R⁸, —SO₂NH₂,—OPO(OR⁹)(OR¹⁰), —OPO(OR⁹)(NH₂), —OPO(OR⁹)—O—PO(OR¹⁰)(OR¹¹),

R¹ to R¹¹ are independently selected from the group consisting ofhydrogen; C₁-C₆ alkyl; C₃-C₆ cycloalkyl; C₂-C₆ alkenyl; C₆ alkynyl;C₅-C₁₀ aryl unsubstituted or substituted with C₁-C₆ alkyl, hydroxyl,C₁-C₆ alkoxyl, 1,3-dioxolanyl, cyano, halo, nitro, trihaloalkyl,carboxyl, C₁-C₆ acyl, C₁-C₆ hydroxyalkyl, anrino, C₁-C₆ alkylamino,C₁-C₆ dialkylamino, C₁-C₆ acylamino, mercapto, C₁-C₆ alkylthio, C₁-C₆mercaptoalkyl, and C₁-C₆ alkxoylcarbonyl; and C₅-C₆ arylalkylunsubstituted or substituted with C₁-C₆ alkyl, hydroxyl, C₁-C₆ alkoxyl,1,3-dioxolanyl, cyano, halo, trihaloalkyl, carboxyl, C₁-C₆ acyl, C₁-C₆hydroxyalkyl, amino, C₁-C₆ alkylamino, C₁-C₆ dialkylamino, mercapto,C₁-C₆ alkylthio, C₁-C₆ mercaptoalkyl, and C₁-C₆ alkxoylcarbonyl; C₁-C₆carboxyalkyl; C₁-C₆ acylamino; C₁-C₆ sulfonatoalkyl; C₁-C₆sulfamylalkyl; and C₁-C₆ phosphonatoalkyl. R¹ and R² or R³ and R⁴ mayoptionally be tethered together to form 3- to 7-membered alicyclic ring.

A preferred embodiment of the present invention is represented byFormula 1,wherein wherein A is —O— or —CH₂—; m and n vary from 0 to 6;pand q vary from 0 to 3; B is —CR³R⁴; D is selected from the groupconsisting of —CO₂R⁵, —OR⁶, and

R¹ to R⁶ are independently selected from the group consisting ofhydrogen; C₁-C₆alkyl, and C₃-C₆ cycloalkyl. R¹ and R² or R³ and R⁴ mayoptionally be tethered together to form 3- to 7-membered alicyclic ring.

Another preferred embodiment of the present invention is represented byFormula 1, wherein A is —O— or —CH₂—; m and n vary from 0 to 6;p and qvary from 0 to 3; B is —CR³R⁴; D is selected from the group consistingof —CO₂R⁵, —OR⁶, and

R¹ to R⁶ are independently hydrogen or C₁-C₆ alkyl.

Another preferred embodiment of the present invention is represented byFormula 1, wherein A —O— or CH₂—; m is 4;n is 4;p varies from 0 to 3;qis 0 or 1; B is —CR³R⁴; D is selected from the group consisting of—CO₂R⁵, —CH₂OR⁶, and

R¹ to R⁴ are methyl groups. R⁵ is hydrogen or an ethyl group. R⁶ ishydrogen.

Another preferred embodiment of the present invention is represented byFormula 1, wherein A is a single bond m is 0 or 1;n is 0 or 1;p is 0 or1;q is 0; B is a single bond; D is —OR⁶; R³ and R⁴ are methyl groups.

The compounds belonging to Formula 1 can be synthesized according to themethod known in the art. The dual prodrug of the present invention canbe prepared by standard methods well known in the art. Alkylation ofα,ω-dihaloalkane 3 with 2 equivalents of the anion 3 (prepared bydeprotonation of ethyl isobutyrate with lithium diisopropylamimde, LDA)gives the key intermediate, the diester 4 (Scheme 1) from which many ofthe prodrugs

of the present invention can be prepared. The camitine prodrugs 6-8 canbe prepared from the diester 4 as shown in Scheme 2. The monoacid5,prepared by careful saponification of

the diester 4,is condensed with carnitine using dicyclohexylcarbodiimide(DCC) in DMF, THF, or DMSO, or water soluble carbodiimides such asethyl-N-(3-dimethylamino) propyl-carbodiimide (EDC). The monoacid 5 canbe reduced with borane-THF to the corresponding alcohol ester, whichthen can be transformed to the dual prodrug 9 by the methods outlined inScheme 1 The acid 5 can also be homologated using the Arndt-Eistert

method and transformed to the chain elongated to the dual prodrug 10.Similarly, the diester 4 can be hydrolyzed to the diacid, homologated atboth ends of the chain by Arndt-Eistert method, and condensed withcarnitine to give the dual prodrugs 11 and 12. Two-carbon

homologation of the diester 4 can be achieved by reducing 4 to thecorresponding diol, converting the diol to the dihalide, alkylating thedihalide with diethyl malonate, and hydrolyzing the tetraester to thehomologated diester 13, which can then be transformed to the carnitinedual prodrug derivatives as described in Scheme 1.

The carnitine-fibrate dual prodrugs can also be prepared by analogousmethods outlined in previous schemes. The gemfibrozil conjugate 17 canbe prepared as outlined in Scheme 3. The starting material 15 can beprepared by the alkylation of ethyl isobutyrate

with THP-protected 3-bromopropanol. The anion 18 can be prepared byalkylating the phenol 16 with ethyl 2-bromopropionate followed bydeprotonation with lithium diisopropylamide.

Compounds of the present invention may exist as as a single stereoisomeror as mixture of enantiomers and diastereomers whenever chiral centersare present. Individual stereoisomers can be isolated by the methodswell known in the art: diastereomers can be separated by standardpurification methods such as fractional crystallization orchromatography, and enantiomers can be separated either by resolution orby chromatography using chiral columns.

The pharmaceutical composition may also contain physiologicallytolerable diluents, carriers, adjuvants, and the like. The phrase“pharmaceutically acceptable” means those formulations which are, withinthe scope of sound medical judgment, suitable for use in contact withthe tissues of humans and animals without undue toxicity, irritation,allergic response and the like, and are commensurate with a reasonablebenefit/risk ratio. Pharmaceutically acceptable salts are well-known inthe art, and are described by Berge et al. [20], incorporated herein byreference. Representative salts include, but are not limited to acetate,adipate, alginate, citrate, aspartate, benzoate, benzenesulfonate,chloride, bromide, bisulfate, butyrate, camphorate, camphor sulfonate,gluconate, glycerophosphate, hemisulfate, heptanoate, hexanoate,fumarate, maleate, succinate, oxalate, citrate, hydrochloride,hydrobromide, hydroiodide, lactate, maleate, nicotinate,2-hydroxyethansulfonate (isothionate), methane sulfonate, 2-naphthalenesulfonate, oxalate, palmitoate, pectinate, persulfate,3-phenylpropionate, picrate, pivalate, propionate, tartrate, phosphate,glutamate, bicarbonate, p-toluenesulfonate, undecanoate, lithium,sodium, potassium, calcium, magnesium, aluminum, ammonium, tetramethylammonium, tetraethylammonium, methylammonium, dimethylammonium,trimethylammonium, triethylammonium, diethylammonium, and ethylammonium,and the like.

The pharmaceutical compositions of this invention can be administered tohumans and other mammals enterally or parenterally in a solid, liquid,or vapor form. Enteral route includes, oral, rectal, toipical, buccal,and vaginal administration. Parenteral route intravenous, intramuscular,intraperitoneal, intrasternal, and subcutaneous injection or infusion.The compositions can also be delivered through a catheter for localdelivery at a target site, via an intracoronary stent (a tubular devicecomposed of a fine wire mesh), or via a biodegradable polymer.

The active compound is mixed under sterile conditions with apharmaceutically acceptable carrier along with any needed preservatives,excipients, buffers, or propellants. Opthalmic formulations, eyeointments, powders and solutions are also contemplated as being withinthe scope of this invention. Actual dosage levels of the activeingredients in the pharmaceutical formulation can be varied so as toachieve the desired therapeutic response for a particular patient. Theselected dosage level will depend upon the activity of the particularcompound, the route of administration, the severity of the conditionbeing treated, and prior medical history of the patient being treated.However, it is within the skill of the art to start doses of thecompound at levels lower than required to achieve the desiredtherapeutic effect and to increase it gradually until optimaltherapeutic effect is achieved. The total daily dose of the compounds ofthis invention administered to a human or lower animal may range fromabout 0.0001 to about 1000 mg/kg/day. For purposes of oraladministration, more preferable doses can be in the range from about0.001 to about 5 mg/kg/day. If desired, the effective daily dose can bedivided into multiple doses for purposes of administration;consequently, single dose compositions may contain such amounts orsubmultiples thereof to make up the daily dose.

The phrase “therapeutically effective amount” of the compound of theinvention means a sufficient amount of the compound to treat disorders,at a reasonable benefit/risk ratio applicable to any medical treatment.It will be understood, however, that the total daily usage of thecompounds and compositions of the present invention will be decided bythe attending physician within the scope of sound medical judgment. Thespecific therapeutically effective dose level for any particular patientwill depend upon a variety of factors including the disorder beingtreated, the severity of the disorder; activity of the specific compoundemployed; the specific composition employed, age, body weight, generalhealth, sex, diet of the patient; the time of administration, route ofadministration, and rate of excretion of the specific compound employed,and the duration of the treatment. The compounds of the presentinvention may also be administered in combination with other drugs ifmedically necessary.

Compositions suitable for parenteral injection may comprisephysiologically acceptable, sterile aqueous or nonaqueous solutions,dispersions, suspensions or emulsions and sterile powders forreconstitution into sterile injectable solutions or dispersions.Examples of suitable aqueous and nonaqueous carriers, diluents, solventsor vehicles include water, ethanol, polyols (propyleneglycol,polyethyleneglycol, glycerol, and the like), vegetable oils (such asolive oil), injectable organic esters such as ethyl oleate, and suitablemixtures thereof. These compositions can also contain adjuvants such aspreserving, wetting, emulsifying, and dispensing agents. Prevention ofthe action of microorganisms can be ensured by various antibacterial andantifungal agents, for example, parabens, chlorobutanol, phenol, sorbicacid, and the like. It may also be desirable to include isotonic agents,for example sugars, sodium chloride and the like.

Suspensions, in addition to the active compounds, may contain suspendingagents, as for example, ethoxylated isostearyl alcohols, polyoxyethylenesorbitol and sorbitan esters, microcrystalline cellulose, aluminummetahydroxide, bentonite, agar-agar and tragacanth, or mixtures of thesesubstances, and the like. Prolonged absorption of the injectablepharmaceutical form can be brought about by the use of agents delayingabsorption, for example, aluminum monostearate and gelatin. Properfluidity can be maintained, for example, by the use of coating materialssuch as lecithin, by the maintenance of the required particle size inthe case of dispersions, and by the use of surfactants. In some cases,in order to prolong the effect of the drug, it is desirable to slow theabsorption of the drug from subcutaneous or intramuscular injection.This can be accomplished by the use of a liquid suspension ofcrystalline or amorphous material with poor water solubility. The rateof absorption of the drug then depends upon its rate of dissolutionwhich, in turn, may depend upon crystal size and crystalline form.Alternatively, delayed absorption of a parenterally administered drugform is accomplished by dissolving or suspending the drug in an oilvehicle.

Injectable depot forms are made by forming microencapsule matrices ofthe drug in biodegradable polymers such as polylactide-polyglycolide.Depending upon the ratio of drug to polymer and the nature of theparticular polymer employed, the rate of drug release can be controlled.Examples of other biodegradable polymers include poly(orthoesters) andpoly(anhydrides). Depot injectable formulations are also prepared byentrapping the drug in liposomes or microemulsions which are compatiblewith body tissues. The injectable formulations can be sterilized, forexample, by filtration through a bacterial-retaining filter or byincorporating sterilizing agents in the form of sterile solidcompositions which can be dissolved or dispersed in sterile water orother sterile injectable medium just prior to use.

Dosage forms for topical administration include powders, sprays,ointments and inhalants. Solid dosage forms for oral administrationinclude capsules, tablets, pills, powders and granules. In such soliddosage forms, the active compound may be mixed with at least one inert,pharmaceutically acceptable excipient or carrier, such as sodium citrateor dicalcium phosphate and/or a) fillers or extenders such as starches,lactose, sucrose, glucose, mannitol, and silicic acid; b) binders suchas carboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidone,sucrose and acacia; c) humectants such as glycerol; d) disintegratingagents such as agar-agar, calcium carbonate, potato or tapioca starch,alginic acid, certain silicates and sodium carbonate; e) solutionretarding agents such as paraffin; f) absorption accelerators such asquaternary ammonium compounds; g) wetting agents such as cetyl alcoholand glycerol monostearate; h) absorbents such as kaolin and bentoniteclay and i) lubricants such as talc, calcium stearate, magnesiumstearate, solid polyethylene glycols, sodium lauryl sulfate and mixturesthereof. In the case of capsules, tablets and pills, the dosage form mayalso comprise buffering agents. Solid compositions of a similar type mayalso be employed as fillers in soft and hard-filled gelatin capsulesusing such excipients as lactose or milk sugar as well as high molecularweight polyethylene glycols and the like. The solid dosage forms oftablets, dragees, capsules, pills and granules can be prepared withcoatings and shells such as enteric coatings and other coatingswell-known in the pharmaceutical formulating art. They may optionallycontain opacifying agents and may also be of a composition such thatthey release the active ingredient(s) only, or preferentially, in acertain part of the intestinal tract, optionally, in a delayed manner.Examples of embedding compositions which can be used include polymericsubstances and waxes. The active compounds can also be inmicro-encapsulated form, if appropriate, with one or more of theabove-mentioned excipients.

Liquid dosage forms for oral administration include pharmaceuticallyacceptable emulsions, solutions, suspensions, syrups and elixirs. Inaddition to the active compounds, the liquid dosage forms may containinert diluents commonly used in the art such as, for example, water orother solvents, solubilizing agents and emulsifiers such as ethylalcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzylalcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol,dimethyl formamide, oils (in particular, cottonseed, groundnut, corn,germ, olive, castor and sesame oils), glycerol, tetrahydrofurfurylalcohol, polyethylene glycols and fatty acid esters of sorbitan andmixtures thereof. Besides inert diluents, the oral compositions may alsoinclude adjuvants such as wetting agents, emulsifying and suspendingagents, sweetening, flavoring and perfuming agents.

Compositions for rectal or vaginal administration are preferablysuppositories which can be prepared by mixing the compounds of thisinvention with suitable non-irritating excipients or carriers such ascocoa butter, polyethylene glycol or a suppository wax which are solidat room temperature but liquid at body temperature and therefore melt inthe rectum or vaginal cavity and release the active compound.

The present invention also provides pharmaceutical compositions thatcomprise compounds of the present invention formulated together with oneor more non-toxic pharmaceutically acceptable carriers. Compounds of thepresent invention can also be administered in the form of liposomes. Asis known in the art, liposomes are generally derived from phospholipidsor other lipid substances. Liposomes are formed by mono- ormulti-lamellar hydrated liquid crystals which are dispersed in anaqueous medium. Any non-toxic, physiologically acceptable andmetabolizable lipid capable of forming liposomes can be used. Thepresent compositions in liposome form can contain, in addition to acompound of the present invention, stabilizers, preservatives,excipients and the like. The preferred lipids are natural and syntheticphospholipids and phosphatidyl cholines (lecithins) used separately ortogether. Methods to form liposomes are known in the art [21],incorporated herein by reference.

The Examples which follow are presented to describe preferredembodiments and utilities of the invention and are not meant to limitthe invention unless otherwise stated in the claims appended hereto. Thedescription is intended as a non-limiting illustration, since manyvariations will become apparent to those skilled in the art in viewthereof. It is intended that all such variation within the scope andspirit of the appended claims be embraced thereby. Changes can be madein the composition, operation, and arrangement of the method of thepresent invention described herein without departing from the conceptand scope of the invention as defined in the claims.

EXAMPLE 1 Preparation of Ester Dual Prodrug 6 Wherein m=n=4,and p=q=0

Step 1. A solution of 12.8 g (0.1 1 mole) of ethyl isobutyrate in 130 mLof dry THF is cooled to −30° C., and a 2M solution (0.105 mole) oflithium diisopropylamide in heptane is added slowly keeping thetemperature at −30° C. After stirring at this temperature for 30minutes, a solution of 9.95 g (0.05 mole) of bis-(4-chlorobutyl)ether in100 mL of dry THF is added. The suspension is stirred and allowed towarm to room temperature. It is cooled to 5 deg. C., and quenched withslow addition of 50 mL of water with vigorous stirring. The organiclayer is separated, and the aqueous layer extracted with toluene orheptane. The combined organic layers are dried (optional), overanhydrous MgSO₄, and then evaporated to give a white solid, which ispurified by recrystallization from toluene/heptane or THF/heptane togive the diester 4, wherein m=n=4, and p=q=0.

Step 2: The diester from Step 1 (12.11 g, 0.05 mole) is dissolved in 100mL of absolute ethanol and a solution of 0.5 mole of KOH in 50 mL ofabsolute ethanol is added. After stirring for 18 hours, the solvent isremoved, and the residue acidified with cold 6N HCl to pH 1. Theprecipitate is collected and washed thoroughly with water and heptane,and dried to give a white solid. It is further purified byrecrystallization from aqueous ethanol to give 8-9 g of mono acid monoester 5,wherein m=n=4,and p=q=0. The monoacid monoester can be thencondensed with dl- or 1-carnitine as described below.

Alternatively, the crude mono acid potassium salt after saponification,is stirred in toluene, and all residual ethanol is removed by azeotropicdistillation. The remaining dry solid is suspended in dry DMF andstirred with an equivalent of oxalyl chloride. The precipitated KCl isfiltered off and the filtrate, the monoester-monoacid chloride whereinm=n=4, and p=q=0, is used as such in the coupling reaction with dl- or1-carnitine as described below.

Step 3: The monoacid ethyl ester (5.35 g, 0.025 mole) from Step 2 isdissolved in 75 mL of dry THF. Then 1-hydroxybenzotriazole is added(0.34 g, 0.0025 mole) followed by dry L-carnitine or DL-carnitine (4.43g, 0.0275 mole) dissolved in 20 mmL of DMF is added. The solution iscooled to 0° C., and a 1 M solution of dicyclohexylcarbodiimide inCH₂Cl₂ (0.025 mole) is slowly added with stirring, The precipitateddicyclohexyl urea is filtered off, and the filtrate is acidified to pH8. The precipitated product 6 is collected as an internal salt, which isrecrystallized from aqueous ethanol to give a pure product.Alternatively, the pH above may be adjusted to 0-1 with 6N HCL whilekeeping cold. The final prodrug product 6, is then obtained as ahydrochloride salt.

Alternatively, the acid chloride Step 2 above is dissolved in 50 mL ofTHF or benzene, and 10% v/v of DMF. The solution is treated with anequivalent amount of L-carnitine or DL-carnitine, followed by anequivalent amount of triethylamine or diisopropylethyl amine and acatalytic amount of DMAP. When the reaction is complete, the solid iscollected, dissolved in water, and the product isolated as describe inthe previous paragraph.

EXAMPLE 2 Preparation of Acid Dual Prodrug 7, Wherein m=n=4, and p=q=0

The ester prodrug 6, obtained in Example 1, is dissolved in 1 equivalentof aqueous sodium hydroxide at 0-5° C. When all the ethyl ester hashydrolyzed (indicated by nmr of a CHCl₃ extract), the pH is adjusted to4-5 to precipitate the acid prodrug 7, which is collected andrecrystallized from aqueous methanol.

EXAMPLE 3 Preparation of Bis(Carnitine) Dual Prodrug 8, Whereinm=n=4,and p=q=0

The acid prodrug 7 from Example 2 (0.025 mole) is dissolved in 75 mL ofdry THF. Then 1-hydroxybenzotriazole is added (0.0025 mole) followed bydry L-carnitine or DL-carnitine (0.0275 mole) dissolved in 20 mL of DMFis added. The solution is cooled to 0° C., and a 1M solution ofdicyclohexylcarbodiimide in CH₂Cl₂ (0.025 mole) is slowly added withstirring. The precipitated dicyclohexyl urea is filtered off, and thefiltrate is acidified to pH 8. The precipitated product 8 is collectedas an internal salt, which is recrystallized from aqueous ethanol or anyother suitable solvent.

EXAMPLE 4 Conversion of the Acid Prodrug 7 into the CorrespondingAlcohol Prodrug, Wherein m=n=4,and p=q=0,and B is —CH₂OH

The acid prodrug 7 is dissolved in THF/10% DMF, and an equivalent ofpivaloyl chloride is added at 0-5° C. followed by an equivalent oftriethyl amine. The triethylamine hydrochloride is filtered off and thefiltrate of mixed anhydride is reacted with an excess of sodiumborohydride solution in THF. The reaction mixture is quenched withacetic acid, and the solution diluted with heptane to precipitate theproduct. The product is collected and purified by recrystallization fromaqueous methanol or any other suitable solvent.

EXAMPLE 5 Preparation of Ester Prodrug 11, Wherein m=n=4 and p=q=1

Step 1. A one molar solution of Grignard reagent BrMg(CH₂)₄—O—(CH₂)₄MgBrin diethyl ether is prepared from Bis(4-bromobutyl)ether, and magnesiumturnings in the usual manner under an inert atmosphere. To this solutionis slowly added a solution of 400.46 g (2 moles) of diethylisopropylidinemalonate dissolved in 2 liter of dry diethylether. Thereaction mixture is refluxed 12 hours and the mixture treated withaqueous ammonium chloride. The ether solution is separated from thesalts, and concentrated to dryness. The residue is purified bydistillation using a wiped-film evaporator to give the intermediatetetraethylester, (EtOOC)₂CHC(CH₃)₂(CH₂)₄—O—(CH₂)₄C(CH₃)₂CH(COOEt)₂.

Step 2. The purified tetraethyl ester from Step 1 above is dissolved inabsolute ethanol, and treated with 2.1 equivalents of KOH in absoluteethanol. The mixture is stirred at 25-40° C. till the pH is about 9. Thesolvent is removed under vacuum and the residue heated in an oil bath at200° C. until gas evolution has ceased. The residue is recrystallized togive the pure diester EtOOCCH₂C(CH₃)₂(CH₂)₄—O—(CH₂)₄C(CH₃)₂CH₂COOEt.

Step 3. The compound Step 2 above is dissolved in absolute ethanol, andtreated with 1 equivalent or 5% molar excess of KOH in absolute ethanol.Whenthe hydrolysis is complete, the solvent is removed in vacuum, theresidue dissolved in cold water, and the pH adjusted to 1,to precipitatea white solid of mono acid mono ester, which is collected and purifiedby recrystallization to give pureEtOOCCH₂C(CH₃)₂(CH₂)₄—O—(CH₂)₄C(CH₃)₂CH₂COOH.

Step 4. The final ester prodrug 11 is prepared by the same procedure asdescribed in Example 1, Step 3.

EXAMPLE 6 Preparation of the Ester Dual Prodrug 10, Wherein m=n=4p=0,and g =1

Step 1. A solution of t-butyl isobutyrate (0.11 mole) in 130 mL of dryTHF is cooled to −30° C., and a 2M solution (0.105 mole) of lithiumdiisopropylamide in heptane is added slowly keeping the temperature at−30° C. After stirring at this temperature for 30 minutes, a solution of1,4-dibromobutane (0.05 mole) in 100 mL of dry THF is added. Thesuspension is stirred and allowed to warm to room temperature. It iscooled to 5° C., and quenched with slow addition of 50 mL of water withvigorous stirring. The organic layer is separated, and the aqueous layerextracted with toluene or heptane. The combined organic layers are dried(optional), over anhydrous MgSO₄, and then evaporated to give a whitesolid, which is purified by recrystallization from toluene/heptane orTHF/heptane to give the bromoester, t-BuOOCC(CH₃)₂(CH₂)₄Br.

Step 2. A one molar solution of Grignard reagentTHP—O(CH₂)₄—O—(CH₂)₄MgBr in diethyl ether is prepared fromTHP—O(CH₂)₄—O—(CH₂)₄Br and magnesium turnings in the usual manner underan inert atmosphere. To this solution is slowly added a solution of 1mole of diethyl isopropylidinemalonate dissolved in 2 liter of drydiethylether. The reaction mixture is refluxed 12 hours and the mixturetreated with aqueous ammonium chloride. The ether solution is separatedfrom the salts, and concentrated to dryness. The residue is purified bydistillation using a wiped-film evaporator to give the diethylester,THP—O(CH₂)₄C(CH₃)₂CH(COOEt)₂. The tetrahydropyranyl group is thenremoved by treating the above THP ether with IN HCl in THF followed byusual workup to give the corresponding alcoholHO(CH₂)₄C(CH₃)₂CH(COOEt)₂.

Step 3. The diester from Step 2 above is dissolved in absolute ethanoland treated with 1.1 equivalents of KOH in absolute ethanol. The mixtureis stirred at 25-40° C. till the pH is about 9. The solvent is removedunder vacuum and the residue heated in an oil bath at 200° C. until gasevolution has ceased. The residue is recrystallized to give the puremonoester HO(CH₂)₄C(CH₃)₂CH₂COOEt.

Step 4. A solution of the alcohol from Step 3 (0.010 mol) in dry THF (20mL) is cooled to 0° C. and carefully treated with 1.2 equivalents ofsodium hydride (60% suspension in oil) in an inert atmosphere. Afterstirring at this temperature for 30 minutes, a solution of the bromidefrom Step 1 (0.011 mol) in THF (20 mL) is added dropwise. After theaddition is complete, the entire mixture is heated under reflux for 24hours. After cooling, the reaction mixture is poured onto water andextracted with methylene chloride. The organic layer is separated,washed with water, dried over MgSO₄, filtered, and the filtrate taken todryness. The crude product is then treated with 50% trifluoroacetic acidin methylene chloride and kept at ambient temperature for 1 hour.Thereafter, the reaction mixture is poured onto water and extracted withmethylene chloride. The organic layer is separated, washed with water,dried over Na₂SO4,filtered, and the filtrate taken to dryness. The crudemonoacid, HOOCC(CH₃)₂(CH₂)₄—O—(CH₂)₄C(CH₃)₂CH₂COOEt is purified byrecrystallization or chromatography.

Step 5. The final ester prodrug 10 is prepared by the same procedure asdescribed in Example 1, Step 3.

EXAMPLE 7 Preparation of the Ester Dual Prodrug 17 Wherein A and D areSingle Bonds, m=n=q=0,and 4,p=3.and B is —OR⁶

Step 1. Alkylation of 3-bromopropanol THP ether (10 mmol) with ethylisobutyryl anion is carried out in the same manner as described in Step1, Example 1. The alkylated product is then dissolved in THF (20 mL) andtreated with 2M HCl (10 mL) and stirred at ambient temperature for 4hours. The solvent and excess HCl is removed by evaporation in vacuo andthe residue is purified by high vacuum distillation to give pure ethyl5-hydroxy-2-dimethylpentanoate.

Step 2. A solution of the alcohol from Step 1 (10 mmol) andtriethylamine (15 mmol) in dry THF (20 mL) is cooled to 0° C. andcarefully treated with methanesulfonyl chloride (11 mmol) and stirred atambient temperature for 4 hours. The reaction mixture is poured ontowater and extracted with methylene chloride. The organic layer isseparated, washed with water, dried over MgSO₄, filtered, and thefiltrate taken to dryness. The crude material is used as such in thenext step.

Step 3. A mixture of the mesylate from Step 2 (10 mmol) and2,5-dimethylphenol (10 mmol), and finely-ground anhydrous potassiumcarbonate (15 mmol) in glyme (20 mL) is heated under reflux for 8 hours.The reaction mixture is filtered hot and the filtrate evaporated invacuo. The residue is purified by chromatography or recrystallization togive the ethyl ester.

Steps 4 and 5. The ethyl ester is then saponified according to theprocedure described in Step 2 and condensed with carnitine according tothe procedure described in Step 3, Example 1 to give the desired dualprodrug 17.

EXAMPLE 8 Preparation of the Ester Dual Prodrug 17, Wherein A and D areSingle Bonds m=n=p=q=0; and B is OR⁶

Step 1. A solution of ethyl 2-methyl-3-(2,5-dimethyl)phenoxyacetate(0.11 mole) in 130 mL of dry THF is cooled to −30° C., and a 2M solution(0.105 mole) of lithium Diisopropylamide in heptane is added slowlykeeping the temperature at −30° C. After stirring at this temperaturefor 30 minutes, a solution of methyl iodide (0.05 mole) in 100 mL of dryTHF is added. The suspension is stirred and allowed to warm to roomtemperature. It is cooled to 5° C., and quenched with slow addition of50 mL of water with vigorous stirring. The organic layer is separated,and the aqueous layer is extracted with toluene or heptane. The combinedorganic layers are dried (optional), over anhydrous MgSO4,and thenevaporated to give a white solid, which is purified by recrystallizationfrom toluene/heptane or THF/heptane to give the ethyl2,2-dimethyl-3-(2,5-dimethyl)-phenoxyacetate.

Step 2-4. The conversion of the ester from Step 1 to the final compound19 is carried out in the same manner as described in Steps 3-5, Example7.

References

-   1. A. Ziegler, K. Mohr, and E. Bieger. Color Atlas of Pharmacology,    2^(nd) Edition,pp. 154-157. Thieme Publishers, 2000.-   2. Scandinavian Simvastatin Study Group. Lancet 1994, 344, 1383.-   3. NCEP Panel. Circulation 1994, 89, 1329.-   4. C. Carazza. U. S. Pat. No. 4,255,449, 1981.-   5. M. Ramacci. U. S. Pat. No. 4,315,944, 1982.-   6. N. Silliprandi. Hypolipidemic Drugs. G. Ricci (Ed.). New York:    Ravan, 1982.-   7. N. Yamazaki. Lipid 1990, 1(2).-   8. De Pauly et al. American Journal of Kidney Diseases 2003, 41(4).-   9. M. Calvari et al. Basic Research in Cardiology 2000, 95(2), 75.-   10. B. Cianciaruso et al. Nephrology 2002, 137, 426.-   11. L. R. Wiseman, R. N. Brogden. Drugs and Aging 1998.-   12. R. Ferrari, I Anand. Developments in Cardiovascular Medicine    1995, 162, 323.-   13. J. W. Pettegraw, R. J. McClure. Expert Review of    Neurotherapeutics 2002, 2(5), 647.-   14. R. C. Anderson. Curr. Pharm. Des. 1998,4, 1-15.-   15. B. Stales, J. Dallongville, J. Anwerx, K. Shoonjans, E.    Lieterdorf, J. C. Furchart. Circulation 1998, 98, 2088.-   16. H. J. Harwood, E. S. Hamanaka. Emerging Drug 1998, 3, 147.-   17. C. L. Bisgaier, P. L. Crerager, A. R. Saltiel, S. R.    Tafuiri. U. S. Pat. No. 5,756,544, 1998.-   18. J. Bar-Tana, U. S. Pat. No. 4,689,344, 1987.-   19. J. Bar-Tana et al. U. S. Pat. No. 4,711,896, 1987.-   20. S. M. Berge et al. J. Pharmaceutical Sciences 1977, 66, 1 et    seq.-   21. Prescott, Ed., Methods in Cell Biology, Volume XIV, pp.33 et    seq. Academic Press, New York, 1976.

1. A dual prodrug compound or a pharmaceutically acceptable salt thereofof Formula 1,

wherein A is a single bond, —O—, or —CH₂—; m and n vary from 1 to 15; pand q vary from 0 to 1; B is —CR³R⁴; D is selected from the groupconsisting of —CO₂R⁵—OR⁶, —OCOR⁷, —SO₃R⁸, —SO₂NH₂, —OPO(OR⁹)(OR¹⁰),—OPO(OR⁹)(NH₂), —OPO(OR⁹)—O—PO(OR¹⁰)(OR¹¹),

wherein R¹ to R⁴ are independently selected from C₁-C₆ alkyl; and R⁵ toR¹¹ are independently selected from the group consisting of hydrogen;C₁-C₆ alkyl; C₃-C₆ cycloalkyl; C₂-C₆ alkenyl; C₆ alkynyl; C₅-C₁₀ arylunsubstituted or substituted with C₁-C₆ alkyl, hydroxyl, C₁-C₆ alkoxyl,1,3-dioxolanyl, cyano, halo, nitro, trihaloalkyl, carboxyl, C₁-C₆ acyl,C₁-C₆ hydroxyalkyl, amino, C₁-C₆ alkylamino, C₁-C₆ dialkylamino, C₁-C₆acylamino, and C₁-C₆ alkxoylcarbonyl; C₅-C₆ arylalkyl unsubstituted orsubstituted with C₁-C₆ alkyl, hydroxyl, C₁-C₆ alkoxyl, 1,3-dioxolanyl,cyano, halo, trihaloalkyl, carboxyl, C₁-C₆ acyl, C₁-C₆ hydroxyalkyl,amino, C₁-C₆ alkylamino, C₁-C₆ dialkylamino, and C₁-C₆ alkxoylcarbonyl;C₁-C₆ carboxyalkyl; C₁-C₆ acylamino; C₁-C₆ sulfonatoalkyl; C₁-C₆sulfamylalkyl; and C₁-C₆ phosphonatoalkyl.
 2. The compound of claim 1,wherein A is a single bond, —O—, or —CH₂—; m and n vary from 1 to 6;pand q vary from 0 to 1; B is —CR³R⁴; D is selected from the groupconsisting of —CO₂R⁵,—OR⁶,and

and R¹ to R⁴ are independently selected from the group consisting ofC₁-C₆ alkyl, and R⁵ and R⁶ are independently selected from the groupconsisting of hydrogen, C₁-C₆ alkyl, and C₃-C₆ cycloalkyl.
 3. Thecompound of claim 1, wherein A is —O—; m is 4; n is 4; p varies from 0to 1; q is 0 or 1; B is —CR³R⁴; D is selected from the group consistingof —CO₂R⁵, —OR⁶, and

and R¹ to R⁴ are methyl groups; R⁵ is hydrogen or an ethyl group; and R⁶is hydrogen.
 4. The compound of claim 1, wherein A is —CH₂—; B is—CR³R⁴; m is 4; n is 5; p varies from 0 to 1; q is 0 or 1; D is selectedfrom the group consisting of —CO₂R⁵, —OR⁶, and

and R¹ to R⁴ are methyl groups; R⁵ is hydrogen or an ethyl group; and R⁶is hydrogen.